Our proposed research is primarily aimed at providing a mechanistic understanding of the kinetics of dissolution of cholesterol gallstones in bile from the physical chemical standpoint. Effort is being directed toward establishing correlations between physical models and in vitro experimental results with gallstones and with cholesterol monohydrate pellets and single crystals. Special emphasis is being directed toward the understanding of the recently discovered interfacial barrier which appears to rate-limit both the in vitro dissolution of gallstones and cholesterol monohydrate crystals in bile salt lecithin solutions. Attention is also being given to seeking out and studying agents that may be able to counteract the interfacial barrier for gallstone dissolution.